<?php 
//1.使用include引入类文件
include 'Test1.php';//定义的类Test1.php
include 'Test2.php';//定义的类Test2.php

//实例化类
$test1=new Test1;
echo $test1::a();
echo "<br>";
$test2=new Test2;
echo $test2::a();
 
 ?>